To make sure Luisa arrived on time she left 15 minutes early.

Which revised sentence shows the correct punctuation for indicating a pause?

To make sure Luisa arrived on time—she left 15 minutes early.

To make sure Luisa arrived on time-she left 15 minutes early.

To make sure Luisa arrived on time, she left 15 minutes early.

To make sure Luisa arrived on time … she left 15 minutes early.